Several processes require water of high purity. Examples of such processes include semiconductor production and pharmaceutical production. Deionization is a process that incorporates ion exchange processes in order to remove impurities from water. Deionization of water to an electrical resistance of about 18.2 million ohms-cm is known as complete deionization and constitutes “high purity water.”
To perform deionization, water is passed through a resin bed. The resin bed serves to remove impurities. Resin beds have limited functionality, which can be restored by contacting the spent resin with the appropriate acid and/or base to remove the impurities from the spent resin. Regeneration of resins, particularly of mixed bed resins, can be tedious, as it generally requires removal and separation of the resin into the two (or more) individual resins.
Deionization of water generally has been performed in vessels reinforced with mineral fibers (e.g., glass fibers) with a head sealing a single opening of the vessels. The head typically has three ports: an inlet port, an outlet port, and a utility port. The outlet port of the head is generally outfitted with a downpipe and outlet screen to allow deionized water to be forced from the deionization vessel without removing the resin in the process. However, the process of recharging the assembly (i.e., removing spent resin from the vessel and replacing it with functional resin) with the head attached to the vessel is inefficient, usually requiring human intervention to remove the spent resin. For example, the assembly may need to be inverted to allow spent resin to pour from one or more of the openings of the head. Furthermore, delivery of a new functional resin bed using such a head configuration provides inconsistent and unreliable results at least in part because the new functional resin bed is delivered from the utility port, which without modification, is incapable of delivering a base layer of the functional resin to the lower portion of the vessel.
Often assemblies recharged in this manner are incapable of meeting the about 18.2 million ohms-cm resistance quality standard required of deionized water for certain applications. Recharged assemblies are not put into service for these certain applications unless the recharged assemblies can achieve the resistance quality standard and must be “re-recharged,” which is no more reliable than the previous recharging.